Electric apparatus and control method therefor

ABSTRACT

An electric apparatus for controlling movement of a target object by performing first and second feedback controls, based on a detection signal obtained from detecting the movement of the target object, generates an operation quantity on the target object based on first and second operation quantities for the second feedback control if one of a predetermined target value and an estimated first state quantity of the target object is higher than a first threshold value, and generates the operation quantity on the target object using only the first operation quantity from among the first and the second operation quantities if one of the target value and the first state quantity of the target object is lower than the first threshold value.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an electric apparatus and a controlmethod therefor, and particularly to a technique of controlling drivingof a moving object such as the carriage of a serial type printingapparatus.

Description of the Related Art

As for driving of a carriage that reciprocally moves by a motor in aserial type printer, feedback control such as PID control using anencoder is common practice. In a serial type inkjet printer, a drivingunit that scans a carriage mounted with a printhead for discharging inkemphasizes a velocity vibration at the time of scanning the carriage tostabilize an ink landing position. Thus, it is required to implementcontrol for stabilizing a velocity vibration of the carriage.

In a printing apparatus and a gain correction method described inJapanese Patent Laid-Open No. 2011-102012, a constant (gain) for PIDcontrol is corrected in accordance with a correction ratio based on avelocity vibration quantity for a predetermined period during which aspecific control target is operated. According to Japanese PatentLaid-Open No. 2011-102012, as the velocity vibration quantity is larger,the correction ratio for PID control can be made smaller. As a result,an excessive vibration is suppressed, thereby making it possible toimplement convergence of the velocity vibration of the control target.

In the printing apparatus and the gain correction method described inJapanese Patent Laid-Open No. 2011-102012, to converge the velocityvibration of the control target, the control gain of the control targetis decreased resultantly. Therefore, although it is possible to suppressan excessive vibration of a control target object, the responsiveness ofthe control target object may be spoiled. That is, compatibility betweentraceability and vibration suppression in a change in state of thecontrol target object may become an issue.

SUMMARY OF THE INVENTION

Accordingly, the present invention is conceived as a response to theabove-described disadvantages of the conventional art.

For example, an electric apparatus and a control method thereforaccording to this invention are capable of achieving compatibilitybetween traceability of feedback control and vibration suppression of acontrol target object.

According to one aspect of the present invention, there is provided anelectric apparatus for controlling movement of a target object,comprising: a detection unit configured to detect the movement of thetarget object; a first estimation unit configured to estimate, based ona detection signal output from the detection unit, a control quantityfor performing first feedback control for the target object at a firstperiod; a second estimation unit configured to estimate, based on thedetection signal output from the detection unit, a first state quantityof the target object and a second state quantity obtained by timedifferentiation of the first state quantity in order to perform secondfeedback control for the target object at a second period shorter thanthe first period; a first generation unit configured to generate a firstoperation quantity for the first feedback control based on the controlquantity estimated by the first estimation unit; a second generationunit configured to generate a second operation quantity for the secondfeedback control based on the first state quantity and the second statequantity estimated by the second estimation unit; and a synthesizingunit configured to generate an operation quantity on the target object,wherein if one of a predetermined target value and the first statequantity of the target object estimated by the second estimation unit islarger than a first threshold value, the synthesizing unit generates theoperation quantity on the target object based on the first operationquantity and the second operation quantity, and if one of the targetvalue and the first state quantity of the target object is smaller thanthe first threshold value, the synthesizing unit generates the operationquantity on the target object using only the first operation quantityout of the first operation quantity and the second operation quantity.

According to another aspect of the present invention, there is provideda control method for an electric apparatus for controlling movement of atarget object, comprising: detecting the movement of the target object;estimating, based on a detection signal acquired in the detecting, acontrol quantity for performing first feedback control for the targetobject at a first period; estimating, based on the detection signalacquired in the detecting, a first state quantity of the target objectand a second state quantity obtained by time differentiation of thefirst state quantity in order to perform second feedback control for thetarget object at a second period shorter than the first period;generating a first operation quantity for the first feedback controlbased on the estimated control quantity; generating a second operationquantity for the second feedback control based on the estimated firststate quantity and the estimated second state quantity; and generatingan operation quantity on the target object, wherein in the generatingthe operation quantity, if one of a predetermined target value and theestimated first state quantity of the target object is larger than afirst threshold value, the operation quantity on the target object isgenerated based on the first operation quantity and the second operationquantity, and if one of the target value and the first state quantity ofthe target object is smaller than the first threshold value, theoperation quantity on the target object is generated using only thefirst operation quantity out of the first operation quantity and thesecond operation quantity.

The invention is particularly advantageous since it is possible toachieve compatibility between traceability of feedback control andvibration suppression of a control target object.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are block diagrams each showing a feedback controlarrangement in a driving control unit of a carriage motor of a printingapparatus;

FIG. 2 is a view showing a two-dimensional coordinate space representingthe relationship between the first and the second state quantities;

FIGS. 3A to 3C are graphs each showing the frequency characteristic of avelocity vibration when a specific external disturbance frequencyexists;

FIG. 4 is a graph showing a velocity vibration suppression ratio inaccordance with the velocity of the control target;

FIG. 5 is a timing chart showing a velocity profile of a carriage as acontrol target;

FIG. 6 is a graph showing a transfer function when the feedback controlarrangement is applied to the driving control unit of the carriagemotor.

FIG. 7 is a perspective view showing the main mechanism part of aninkjet printing apparatus according to an exemplary embodiment of thepresent invention;

FIG. 8 is a block diagram showing an overview of the control arrangementof the printing apparatus shown in FIG. 7;

FIG. 9 is a block diagram for explaining details of carriage drivingcontrol in the printing apparatus shown in FIGS. 7 and 8;

FIG. 10 is a timing chart showing A- and B-phase encoder signals;

FIG. 11 is a flowchart illustrating carriage motor driving control ofreciprocally moving the carriage; and

FIG. 12 is a flowchart illustrating carriage motor driving control ofreciprocally moving the carriage by operating only the second controlunit in accordance with the carriage velocity.

DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiments of the present invention will now be described indetail in accordance with the accompanying drawings.

In the following description, control of driving of a motor that moves acarriage of a serial type printing apparatus as an exemplary example ofan electric apparatus will be exemplified. However, the presentinvention is not limited to the carriage of the printing apparatus, andmotor control according to the present invention is applicable to anyunit that moves an object by driving a motor. For example, in theprinting apparatus, motor control is applicable to control of driving ofa conveyance motor used to convey a print medium such as a print sheet.The present invention also includes a scanner apparatus that opticallyreads an image of an original while moving a CCD line scanner or CIS bydriving a motor.

1. Explanation of Feedback Control

FIGS. 1A and 1B are block diagrams each showing a feedback controlarrangement in a driving control unit of a carriage motor of a printingapparatus. FIG. 1A is a block diagram showing a general controlarrangement. FIG. 1B is a block diagram showing a control arrangementused in this embodiment.

First, the general feedback control arrangement will be described withreference to FIG. 1A.

As shown in FIG. 1A, a detection signal (the position and velocity of acarriage) that detects the state of a control target (for example, acarriage) 21 is output to a control quantity estimation unit (forexample, a CPU) 23 to estimate the control quantity of position/velocityinformation or the like. The control quantity is output to a firstcontrol unit (for example, a carriage driver) 22 to calculate anoperation quantity for converging the control target 21 to a targetvalue. When the operation quantity is output to the control target 21, afeedback control loop is formed.

To stably move the control target, it is necessary to set variousparameters while ensuring an allowance in terms of control inconsideration of the characteristic of the control target. If theallowance is insufficient, a vibration occurs, and an oscillationphenomenon may lead to an uncontrollable state. On the other hand, ifthe allowance is too large, the traceability performance of the controltarget deteriorates but it is unavoidable to impose a restriction on thetraceability performance for vibration suppression.

Next, the feedback control arrangement used in this embodiment will bedescribed with reference to FIG. 1B.

As shown in FIG. 1B, in feedback control, in addition to the feedbackcontrol loop shown in FIG. 1A, another feedback control loop using thedetection signal from the control target 21 is formed. That is, thedetection signal that detects the state of the control target 21 isoutput to the control quantity estimation unit 23 to estimate thecontrol quantity of the position/velocity information of the carriage orthe like. The control quantity is output to the first control unit 22,and the first control unit 22 calculates the first operation quantityfor converging the control target 21 to the target value. Then, thefirst control unit 22 outputs the first operation quantity to thecontrol target 21 via the synthesizing unit 26, thereby forming thefirst feedback loop.

On the other hand, the detection signal that detects the state of thecontrol target 21 is also output to a state quantity estimation unit 25,and the state quantity estimation unit 25 estimates the first and secondstate quantities. The second state quantity is obtained by the timedifferentiation of the first state quantity. More specifically, thefirst and second state quantities are values formed from a combinationof a position and a velocity or a combination of a velocity and anacceleration. These values are output to a second control unit 24. Thesecond control unit 24 calculates the second operation quantity. Next,the second control unit 24 outputs the second operation quantity, and asynthesizing unit 26 synthesizes the first and second operationquantities, and outputs a synthesizing result to the control target 21.The second feedback loop “control target 21→state quantity estimationunit 25→second control unit 24→synthesizing unit 26→control target 21”is formed.

Since the first and second state quantities have the relationshipbetween, for example, the position (x) and velocity (v) of the carriageor between the velocity (v) and acceleration (a) of the carriage, therelationship between the two state quantities (two variables) can berepresented by a two-dimensional space.

FIG. 2 is a view showing a two-dimensional coordinate space representingthe relationship between the first and second state quantities.Referring to FIG. 2, the abscissa defines the first state quantity andthe ordinate defines the second state quantity.

As shown in FIG. 2, two divided regions are defined in advance on theplane, and the plane is divided into two regions by a function called aswitchover line. These divided regions will be referred to as regions 1and 2 hereinafter. The function representing the switchover line is alinear function represented by a relationship “S2=k×S1” where S1represents the first state quantity and S2 represents the second statequantity. Note that k represents a switchover coefficient.

As shown in FIG. 2, with respect to the switchover line, an upper region(white) is region 1 and a lower region (hatched) is region 2. If thereis the relationship between the first and second state quantities inregion 1, a positive operation quantity is output. If there is therelationship between the first and second state quantities in region 2,a negative operation quantity is output. Note that in accordance with anoperation condition, a negative sign may be assigned to region 1 and apositive sign may be assigned to region 2. When the sign is switchedover every time the two regions are crossed, the operation quantityimplements movement corresponding to a switching operation. The secondcontrol unit 24 outputs such operation quantity as the second operationquantity to the control target 21 via the synthesizing unit 26.

The first and second operation quantities are updated asynchronously.The synthesizing unit 26 adds the quantities while adjusting the updatetimings, and outputs an added value as the third operation quantity tothe control target 21.

In this embodiment, if the velocity (v) of the control target 21 ishigher than a predetermined first threshold value (v>v₁), the secondcontrol unit 24 outputs the operation quantity based on theabove-described processing. On the other hand, if the velocity (v) islower than the first threshold value (v₁) (v<v₁), the second controlunit 24 outputs zero (0) as the operation quantity. Note that in thisembodiment, if the velocity is equal to the set first threshold value(v=v₁), the second control unit 24 outputs the operation quantity basedon the above-described processing, similar to the case in which thevelocity (v) is higher than the first threshold value (v>v₁). However,the present invention is not limited to this. That is, if the velocityis equal to the first threshold value (v=v₁), the second control unit 24may output zero as the operation quantity.

The reason why this operation is performed will be described next withreference to the accompanying drawings.

FIGS. 3A to 3C are graphs each showing the frequency characteristic of avelocity vibration when a specific external disturbance frequencyexists.

FIG. 3A shows a result obtained when an actual acceleration matches acalculated acceleration to be used for calculation in the second controlunit 24, and the characteristic is indicated by a broken line in FIG.3A. As shown in FIG. 3A, in the whole frequency band, the velocityvibration is almost zero and a satisfactory result is obtained.

FIG. 3B shows a result obtained when there is a certain delay betweenthe actual acceleration (a) and the calculated acceleration to be usedfor calculation in the second control unit 24, and the characteristic isindicated by a thick solid line in FIG. 3B. Since the acceleration to beused for calculation is calculated as a change quantity (dv/dt) of thevelocity, the delay is larger as the velocity of the control target 21is lower. In the result shown in FIG. 3B, while the velocity vibrationat the external disturbance frequency remains, a velocity vibration at ahigh frequency different from the external disturbance frequency occurs.

FIG. 3C shows a result obtained when a delay in the calculatedacceleration is larger than that in FIG. 3B, that is, the velocity ofthe control target 21 is lower. In this case, while a larger velocityvibration at the external disturbance frequency remains, a velocityvibration at a high frequency becomes larger. As described above, if thevelocity of the control target 21 becomes lower, the feedback controlperformance gradually decreases. Thus, to sufficiently obtain theeffect, the second control unit 24 executes the above-describedoperation when the velocity of the control target 21 is equal to orhigher than the first threshold value. Note that as the velocity of thecontrol target 21 to be compared with the first threshold value, atarget velocity may be used or a detected velocity may be used.

Furthermore, a method of calculating the state quantity in the statequantity estimation unit 25 is changed based on the velocity (v) of thecontrol target 21 and the second threshold value. If the velocity islower than the second threshold value (v<v₂), a calculation count forthe displacement quantity of the control target 21 is increased, ascompared with a case in which the velocity is higher than the secondthreshold value (v>v₂). Note that the second threshold value is largerthan the first threshold value (v₂>v₁). In this embodiment, for example,when the velocity and the acceleration are calculated by detecting theposition of the control target 21 using a linear scale and an encodersensor, if the velocity of the control target 21 is lower than thesecond threshold value, two edges of each of the A- and B-phase encodersignal pulses are used. On the other hand, if the velocity of thecontrol target 21 is higher than the second threshold value, only oneedge of one of the A- and B-phase encoder signal pulses is used. Notethat in this embodiment, if the velocity is equal to the secondthreshold value (v=v₂), the state quantity estimation unit 25 uses onlyone edge of the encoder signal pulse, similar to the case in which thevelocity is higher than the second threshold value (v>v₂). However, thepresent invention is not limited to this. That is, if the velocity isequal to the second threshold value (v=v₂), the state quantityestimation unit 25 may use one edge of one of the A- and B-phase encodersignal pulses.

The reason why this operation is performed will be described withreference to FIG. 4.

FIG. 4 is a graph showing a velocity vibration suppression ratio inaccordance with the velocity of the control target 21.

Referring to FIG. 4, the abscissa represents the velocity (v) of thecontrol target 21 and the ordinate represents a velocity vibrationsuppression ratio of the case in which a state quantity is calculated atthe two edges of each of the A- and B-phase encoder signal pulses withrespect to the case in which a state quantity is calculated at only oneedge of one of the A- and B-phase encoder signal pulses.

Referring to FIG. 4, in a region where the suppression ratio is lowerthan 0, suppression control using the two edges suppresses the velocityvibration more than suppression control using one edge. In a regionwhere the suppression ratio is higher than 0, the suppression controlusing one edge suppresses the velocity vibration more than thesuppression control using the two edges.

It can be understood from the characteristic shown in FIG. 4 that highercontrol performance is obtained by the suppression control using the twoedges up to a given velocity of the control target 21, and highercontrol performance is obtained by the suppression control using oneedge at a velocity higher than the given velocity. This indicates thatit is preferable to suppress a delay caused by calculation by increasingthe detection frequency up to the given velocity. However, thisindicates that if the detection frequency becomes too high, a detectionerror is amplified by a derivative element when calculating a velocityand an acceleration, thereby degrading the performance. In this way,when the velocity of the control target 21 changes and the statedetection frequency of the control target 21 changes, the controlperformance is influenced. Therefore, the state quantity estimation unit25 operates to change the detection frequency, as described above, inaccordance with whether the velocity of the control target 21 is equalto or higher than the second threshold value.

Note that as the velocity (v) of the control target 21 to be comparedwith the second threshold value, a target velocity may be used or animmediately precedingly detected velocity may be used.

An example in which the feedback control shown in FIG. 1B is applied tocontrol of the velocity of the carriage that reciprocates while beingmounted with a printhead in the serial type printing apparatus will nowbe described.

FIG. 5 is a timing chart showing the velocity profile of the carriage asthe control target.

Referring to FIG. 5, the abscissa represents time (t) and the ordinaterepresents the velocity (v) of the carriage. FIG. 5 shows the velocityprofile in which the carriage starts to move from a home position att=t₁, accelerates to reach a velocity v_(c), transitions to constantmovement, and then decelerates to stop at t=t₂. However, the actualcarriage motion is not ideal, and the velocity of the carriagemicro-vibrates due to the influence of an external disturbance or thelike during constant movement. The micro-vibration of the velocityindicates the occurrence of positive and negative accelerations at avery short period.

In FIG. 5, the ideal velocity profile is indicated by a broken line anda micro-velocity vibration during constant movement is indicated by athick solid line.

In the feedback control according to this embodiment, the first controlunit 22 is responsible for control of the velocity profile indicated bythe broken line, and moves the carriage as control target to a targetposition in accordance with a desired acceleration condition andvelocity condition. The first control unit 22 executes PID controlcalculation generally widely used, sets various parameters inconsideration of an allowance in terms of control, determines a controlband, and then implements desired movement while suppressing a vibrationin the control band.

On the other hand, the second control unit 24 is responsible for controlof suppressing a micro-velocity vibration indicated by the thick solidline. The second control unit 24 suppresses a vibration phenomenon(velocity vibration) in a high-frequency band exceeding the control bandof the first control unit 22. To suppress such velocity vibration, it isnecessary to perform, at a short period corresponding to the period ofthe velocity vibration, an operation of giving a positive accelerationas an operation quantity for a negative acceleration that occurs whilegiving a negative acceleration as an operation quantity for a positiveacceleration that occurs. Therefore, since a sufficiently short controlperiod is required to implement the control performance, the secondcontrol unit 24 executes control at a control period at least shorterthan that of the first control unit 22.

When the control period is sufficiently short, the second control unit24 can implement a high-speed switching operation, and can performvibration suppression (velocity vibration suppression) up to a regionexceeding the control band of the first control unit 22. Therefore, evenif the state of the carriage as the control target changes and avibration phenomenon occurs when only feedback control by the firstcontrol unit 22 is performed, the second control unit 24 can suppress avibration to build a stable control system without spoiling thetraceability.

In summary, the role of the first control unit 22 that performs theconventional feedback control is to converge, to the target position,the carriage as the control target having the velocity profile formedfrom acceleration, a constant velocity, and deceleration. The firstcontrol unit 22 forms a feedback loop (first feedback loop) by PIDcontrol using the control quantity formed from the position and velocityinformation of the carriage. On the other hand, the role of the secondcontrol unit 24 is to suppress a micro-velocity vibration of thecarriage that cannot be controlled by the first control unit 22. Thesecond control unit 24 forms a feedback loop (second feedback loop) byhigh-speed switching control using a state quantity formed from acombination of a position and a velocity or a velocity and anacceleration. Therefore, control of the second feedback loop is executedat a calculation period shorter than that of the first feedback loop.

FIG. 6 is a graph showing a transfer function when the above-describedcontrol arrangement is applied to the driving control unit of thecarriage motor. The transfer function outputs a velocity vibrationsuppression gain obtained when an external disturbance is given to thecarriage as the control target. Referring to FIG. 6, the ordinaterepresents a gain (db) as a transfer ratio and the abscissa represents afrequency (Hz).

Referring to FIG. 6, curve C indicated by a broken line represents acharacteristic obtained when only the first control unit 22 is operated.On the other hand, curve D indicated by a thick solid line represents acharacteristic obtained when both the first control unit 22 and thesecond control unit 24 are operated and the synthesizing unit 26generates the third operation quantity. As is apparent by comparingcurves C and D, curve D indicates a small value in a frequency regionwhere the frequency is higher than a frequency f₀, which indicates thatthe external disturbance suppression effect is high. The frequency f₀roughly indicates the control band of the first control unit 22.Therefore, by operating the second control unit 24 together with thefirst control unit 22, a vibration suppression effect is produced in afrequency band (35 Hz to 300 Hz) higher than the control band of thefirst control unit 22.

2. Explanation of Application Example of Feedback Control

A serial type printing apparatus to which control of forming the twofeedback loops explained with reference to FIG. 1B is applied will bedescribed.

<Explanation of Printing Apparatus (FIGS. 7 and 8)>

FIG. 7 is an external perspective view showing the arrangement of theprinting apparatus mounted with an inkjet printhead (to be referred toas a printhead hereinafter) that discharges ink droplets in accordancewith an inkjet method, according to the exemplary embodiment of thepresent invention.

A carriage (moving object) 3 mounted with a printhead 2 is supportedslidably by a guide shaft 4, and reciprocally moves above a print medium(sheet) 1. A carriage motor (DC motor) 5 with a pulley is arranged atone end of the moving range of the carriage 3, an idle pulley 6 isarranged at the other end, and a timing belt 7 is looped between thecarriage motor 5 and the idle pulley 6, thereby connecting the carriage3 to the timing belt 7.

To prevent the carriage 3 from rotating about the guide shaft 4, asupport member 8 installed to extend in parallel to the guide shaft 4 isinstalled, and the carriage 3 is also supported slidably by the supportmember 8. In the printhead 2, a number of print elements are providedand an FFC (Flexible Flat Cable) 11 for supplying the driving signals ofthe print elements from the main body portion of the printing apparatusto the printhead 2 is arranged. The FFC 11 has a long thin film shape, aconductive pattern for transmitting a driving signal is formed in theinside or surface of the FFC 11, and the FFC 11 has flexibility so thatit bends along with the movement of the carriage 3 to move the centralposition of bending.

Furthermore, an ink tank (not shown) is arranged outside the carriage 3,and a tube 12 that supplies, to the printhead 2, ink contained in theink tank is provided. The tube 12 has flexibility so that it bends alongwith the movement of the carriage 3 to move the central position ofbending. A connecting member 10 formed from the FFC 11 and the tube 12is connected between the carriage 3 and a fixing portion 9 of the mainbody 13 of the printing apparatus.

Furthermore, a linear scale 16 that is used to acquire the positioninformation of the carriage 3 is arranged in parallel to the movingdirection (main scanning direction) of the carriage, and is configuredto be read by an encoder sensor 15 attached to the carriage 3. Inkcollection ports 14 a and 14 b for collecting ink preliminarilydischarged by the printhead 2 are provided on both the outsides in thewidth direction of the print medium 1. The preliminary dischargeindicates an operation for discharging, at positions irrelevant toprinting, ink adhered to the distal end portions of nozzles immediatelybefore the start of printing or during execution of printing.

With this arrangement, the carriage 3 reciprocally moves in a direction(main scanning direction) of an arrow A. The print medium 1 is conveyedby a conveyance motor (not shown) in a direction (sub-scanningdirection) of an arrow B vertically intersecting the carriage 3.

FIG. 8 is a block diagram showing the control arrangement of theprinting apparatus shown in FIG. 7.

As shown in FIG. 8, a controller 600 is formed by an MPU 601, a ROM 602,an ASIC (Application Specific Integrated Circuit) 603, a RAM 604, asystem bus 605, an A/D converter 606, and the like. The ROM 602 stores aprogram corresponding to a control sequence (to be described later), arequired table, and other fixed data. Note that a CPU may be used inplace of the MPU 601, and any processor capable of executing processingbased on a program may be used.

The ASIC 603 generates control signals for controlling the carriagemotor 5, a conveyance motor 20, and the printhead 2. The RAM 604 is usedas a loading area of image data, a work area for executing a program,and the like. The system bus 605 interconnects the MPU 601, the ASIC603, and the RAM 604 to exchange data. The A/D converter 606 receives ananalog signal from a sensor group (to be described below), performs A/Dconversion, and supplies a digital signal to the MPU 601.

Referring to FIG. 8, reference numeral 610 denotes a host apparatusserving as an image data supply source. Image data, a command, a status,and the like are transmitted/received between the host apparatus 610 andthe printing apparatus via an interface (I/F) 611 using, for example, aprotocol based on the USB standard.

Furthermore, reference numeral 620 denotes a switch group which isformed from a power switch 621, a print switch 622 used to issue a printstart instruction or the like, a recovery switch 623, and the like.

Reference numeral 630 denotes a sensor group for detecting an apparatusstatus, which is formed from detectors such as the encoder sensor 15, atemperature sensor 632, and the like.

Reference numeral 640 denotes a carriage motor driver that drives thecarriage motor 5 for causing the carriage 3 to reciprocally scan in thedirection of the arrow A; and 642, a conveyance motor driver that drivesthe conveyance motor 20 for conveying a print medium P.

At the time of print scanning by the printhead 2, the ASIC 603 transfersdata for driving the print elements (heaters for discharge) to theprinthead 2 while directly accessing the memory area of the RAM 604. Inaddition, this printing apparatus includes, as a user interface, anoperation panel 18 formed by an LCD or LED. From the viewpoint ofapparatus implementation, the switch group 620 may be included in theoperation panel 18.

The ASIC 603 operates as a calculation processing unit to perform imageprocessing and actuator control, and executes calculation processing byreceiving a command from the MPU 601. Feedback control calculation ispartially executed by the ASIC 603, and details thereof will bedescribed later. The MPU 601 is responsible for part of calculation forfeedback control of the carriage 3, and executes driving calculation ofthe carriage motor 5 in accordance with a print sequence. When the hostapparatus 610 issues a print command via the interface 611, the carriage3 reciprocally operates for a print operation.

3. Details of Feedback Control Arrangement for Carriage Control of

Printing Apparatus

Application of the feedback control arrangement described with referenceto FIG. 1B to carriage driving control in the printing apparatusdescribed with reference to FIGS. 7 and 8 will be described in detail.

FIG. 9 is a block diagram for explaining details of carriage drivingcontrol in the printing apparatus shown in FIGS. 7 and 8.

Accuracy for causing ink to land at a correct position is required forcarriage control of the printing apparatus in order to ensure the printquality by the printhead 2. An ink droplet discharge timing from theprinthead 2 is calculated from the moving velocity (v) of the carriage3, and it is important to minimize a velocity vibration. To achievethis, a vibration target to be suppressed in the feedback controlaccording to this embodiment is the velocity of the carriage. Therefore,the first and second state quantities in the feedback control describedwith reference to FIG. 1B are formed from a combination of the velocityand acceleration of the carriage 3, and are input to the second controlunit 24.

Furthermore, the control target in the feedback control is the carriage3, and the encoder sensor 15 outputs encoder signals to the controlquantity estimation unit 23 and the state quantity estimation unit 25.In general, two A- and B-phase pulse signals whose phases are differentfrom each other by 90° are used as encoder signals. In this embodimentas well, two A- and B-phase pulse signals are used as the encodersignals.

FIG. 10 is a timing chart showing the A- and B-phase encoder signals.

The control quantity estimation unit 23 estimates position informationby counting the pulse signal, and estimates velocity information bymeasuring the pulse width of the pulse signal. This position/velocityinformation or the like is output as a control quantity to a PID controlcalculation unit 36 corresponding to the first control unit 22.

A target value calculation unit 35 generates a target profile for movingthe carriage 3 to a target position in accordance with a desiredacceleration condition and velocity condition, and outputs the targetprofile as a target value. The PID control calculation unit 36 performsPID control calculation using the target value from the target valuecalculation unit 35 and the control quantity from the control quantityestimation unit 23, and outputs a calculation result as the firstoperation quantity.

The encoder signal from the encoder sensor 15 is also output to thestate quantity estimation unit 25. The state quantity estimation unit 25also receives a register setting value output from a preprocessingcalculation unit 38. The register setting value is a value obtained byreplacing, by the preprocessing calculation unit 38, the target valuefrom the target value calculation unit 35 by a value in a unit systemused in the state quantity estimation unit 25. The state quantityestimation unit 25 estimates velocity information and accelerationinformation from the encoder signal, and calculates an error quantitywith respect to the register setting value as an operation target. Avelocity error quantity and acceleration error quantity as the errorquantity are output, as a combination of state quantities in thevelocity dimension and acceleration dimension, to a sliding mode controlcalculation unit 39 corresponding to the second control unit 24.

As described above, in accordance with the velocity (v) of the controltarget 21, the state quantity estimation unit 25 changes the frequencyat which the state quantity is estimated. In this embodiment, if thevelocity (v) of the carriage 3 as the control target 21 is lower thanthe second threshold value (v<v₂), the frequency is changed to a higherone. If the velocity (v) is equal to or higher than the second thresholdvalue, the frequency is changed to a lower one.

More specifically, in the former case (v<v₂), the state quantity isestimated at all the timings of the leading and trailing edges of the A-and B-phase encoder signals. In the latter case (v≥v₂), the statequantity is estimated only at the timing of the leading edge of theA-phase encoder signal. Note that in this embodiment, in the latter case(v≥v₂), a plurality of threshold values may be set, and the statequantity may be calculated at the timings of the leading and trailingedges of only the A-phase encoder signal, as an intermediate casebetween the above two cases.

The sliding mode control calculation unit 39 forms a two-dimensionalplane space of two variables of a velocity error quantity and anacceleration error quantity. Region determination of the two-dimensionalplane described with reference to FIG. 2 is obtained by:S=switchover coefficient x acceleration error quantity+velocity errorquantityIf S>0, the current state quantity is located in region 1 as the upperportion with respect to the switchover line. On the other hand, if S<0,the current state quantity is located in region 2 as the lower portionwith respect to the switchover line. If S=0, S=0 is defined as S>0 orS<0. The sign of the operation quantity is determined based on theregion determination result, and the operation quantity is output as thesecond operation quantity. Note that the switchover coefficient isupdated by the register setting value output from the preprocessingcalculation unit 38.

Furthermore, since, as described above, the second control unit 24outputs the operation quantity based on the calculation processing onlyif the velocity of the control target 21 is equal to or higher than thefirst threshold value, the above-described sliding mode controlcalculation unit 39 is configured in the same manner. If the velocity ofthe control target 21 is lower than the first threshold value, thesliding mode control calculation unit 39 outputs zero. Note that in thisembodiment, if the velocity is lower than the first threshold value, thesliding mode control calculation unit 39 outputs zero by stopping thegeneration of the operation quantity. However, the present invention isnot limited to this embodiment. For example, if the velocity is lowerthan the first threshold value, the sliding mode control calculationunit 39 may generate the operation quantity but may output zero.Furthermore, the case in which the sliding mode control calculation unit39 outputs zero includes not only a case in which a value of zero isoutput but also a case in which no value is output.

The update timings of the first and second operation quantities will nowbe described.

The first operation quantity is updated every time the PID controlcalculation unit 36 is executed. The carriage motor driving control unit(carriage motor driver) of the printing apparatus to which the feedbackcontrol shown in FIG. 1B is applied often executes control calculationat a period of about 1 KHz. On the other hand, the second operationquantity is updated every time the sliding mode control calculation unit39 is executed. A change in pulse of the encoder signal is assumed, andcontrol calculation is executed at a period of about several kHz to 20kHz. For such inputs having an asynchronous relationship, thesynthesizing unit 26 adds the first operation quantity to the secondoperation quantity while adjusting the timings The synthesizing unit 26outputs a PWM signal based on the addition result of the operationquantities to the carriage motor driver 640. The carriage motor driver640 rotates the carriage motor 5, and the carriage 3 moves through thetiming belt 7.

To implement high-speed calculation derived from a change in pulse ofthe encoder signal, it is assumed that the sliding mode controlcalculation unit 39 is executed by hardware such as an ASIC.

Referring to FIG. 9, a range surrounded by a two-dot dashed line isimplemented in the ASIC 603. As is apparent from FIG. 9, the ASIC 603 isresponsible for the functions of the sliding mode control calculationunit 39, the control quantity estimation unit 23, the state quantityestimation unit 25, and the synthesizing unit 26. To the contrary, inFIG. 9, a range surrounded by a thick dotted line is implemented whenthe MPU 601 executes a program. As is apparent from FIG. 9, the MPU 601is responsible for the functions of the PID control calculation unit 36,the target value calculation unit 35, and the preprocessing calculationunit 38.

The reason why the MPU 601 and the ASIC 603 share the feedback controlis that the update period of the information processed in the portionimplemented by the ASIC 603 is shorter than that of the informationprocessed in the portion implemented by the MPU 601.

The preprocessing calculation unit 38 is also executed every time thetarget value calculation unit 35 updates the target value, and thelatest register setting value is set in the register area of the ASIC603. The preprocessing calculation unit 38 performs calculation formanaging, as parameter values, only during the calculation period of thePID control calculation unit 36, some of variable values that changemoment by moment in calculation of the phase switchover line executed bythe sliding mode control calculation unit 39 or estimation calculationof the state quantity estimation unit 25. Execution of all the feedbackcontrol by the ASIC leads to increasing the size of the integratedcircuit, and there is a lack of flexibility and versatility ofprocessing. Thus, in this embodiment, the calculation accuracy and thecircuit scale are compromised, and the preprocessing calculation unit 38of the MPU executes part of calculation at the update timing

A control parameter to be used by the sliding mode control calculationunit 39 may be changed in accordance with the operation state of thecarriage 3. In this case, based on the target value of the target valuecalculation unit 35, a section of one of an acceleration state, aconstant velocity state, and a deceleration state, in which the carriage3 is located is determined. By changing, for each section, theswitchover coefficient to be used to calculate the phase switchoverline, an appropriate switchover line according to a carriage operationcondition is selected to implement rapid convergence.

FIG. 11 is a flowchart illustrating carriage motor driving control ofreciprocally moving the carriage.

When driving control starts, the output of the second control unit 24 isset to zero (0) in step S1. If the output of the second control unit 24is zero, driving of the carriage motor undergoes feedback control onlyby the first control unit 22. In step S2, the two edges of each of theA- and B-phase encoder signal pulses are set to be used for stateestimation calculation so that the estimation calculation frequency ofthe state quantity estimation unit 25 becomes high. In step S3, drivingof the carriage motor 5 starts.

After that, the first control unit 22 performs feedback control so thatthe velocity (v) of the carriage 3 follows the target value. In step S4,it is checked whether the velocity (v) of the carriage 3 as the controltarget is equal to or higher than the first threshold value. Driving ofthe carriage motor 5 is continued until it is determined that thevelocity (v) of the carriage 3 is equal to or higher than the firstthreshold value (v≥v₁). On the other hand, if it is determined that thevelocity (v) of the carriage 3 is equal to or higher than the firstthreshold value (v≥v₁), the process advances to step S5, and processingin the second control unit 24 and operation quantity output processingstart.

In step S6, it is checked whether the velocity (v) of the carriage 3 isequal to or higher than the second threshold value larger than the firstthreshold value. The processing in the second control unit 24 and theoperation quantity output processing are continued until it isdetermined that the velocity (v) of the carriage 3 is equal to or higherthan the second threshold value (v≥v₂). On the other hand, if it isdetermined that the velocity (v) of the carriage 3 is equal to or higherthan the second threshold value (v≥v₂), the process advances to step S7.

In step S7, one edge of the A-phase encoder signal pulse is set to beused for state estimation calculation so that the estimation calculationfrequency of the state quantity estimation unit 25 becomes low. Thus,the estimation frequency in the state quantity estimation unit 25becomes “low”. After that, in step S8, it is checked whether thevelocity (v) of the carriage 3 is lower than the second threshold value.The estimation processing in the state quantity estimation unit 25 atthe low frequency is continued until it is determined that the velocity(v) of the carriage 3 is lower than the second threshold value (v<v₂).On the other hand, if it is determined that the velocity (v) of thecarriage 3 is lower than the second threshold value (v<v₂), the processadvances to step S9.

In step S9, the two edges of each of the A- and B-phase encoder signalpulses are set to be used for state estimation calculation of the statequantity estimation unit 25. Thus, the estimation frequency in the statequantity estimation unit 25 becomes “high”. After that, in step S10, itis checked whether the velocity (v) of the carriage 3 is lower than thefirst threshold value (v<v₁). Estimation in the state quantityestimation unit 25 at the high frequency is continued until it isdetermined that the velocity (v) of the carriage 3 is lower than thefirst threshold value (v<v₁). On the other hand, if it is determinedthat the velocity (v) of the carriage 3 is lower than the firstthreshold value (v<v₁), the process advances to step S11, and theprocessing in the second control unit 24 is stopped to set the operationquantity output to zero.

After that, the first control unit 22 performs feedback control of thecarriage motor 5 until the carriage 3 stops. In step 512, driving of thecarriage motor 5 is stopped, thereby ending one driving controloperation.

Therefore, according to the above-described embodiment, the feedbackcontrol arrangement formed from the first and second control units isapplied to carriage driving control of the printing apparatus. Inaccordance with the carriage velocity, the processing and output of thesecond control unit are controlled and the estimation frequency of thestate quantity estimation unit is switched. Since this can achievecompatibility between traceability and vibration suppression of thecarriage as the control target object of feedback control, carriagedriving control can be performed more precisely, thereby implementinghigh-quality image printing.

Note that in the above-described embodiment, according to the carriagevelocity, control of the operation/stop of the second control unit and achange of the estimation calculation frequency of the state quantityestimation unit 25 are performed. However, the present invention is notlimited to this. One of these operations, for example, only control ofthe operation/stop of the second control unit according to the carriagevelocity may be executed.

In the above embodiment, if the velocity is lower than the firstthreshold value, the operation of the second control unit is stopped toset the output to zero, thereby inputting, to the synthesizing unit 26,only the output (first operation quantity) from the first control unit.As a result, if the velocity is lower than the first threshold value,the synthesizing unit 26 generates the operation quantity of the targetobject using only the first operation quantity. However, the presentinvention is not limited to this. For example, if the velocity is lowerthan the first threshold value, the second control unit generates thesecond operation quantity and outputs it but the synthesizing unit 26may generate the operation quantity of the target object using only thefirst operation quantity without using the input second operationquantity. That is, in either case, in the embodiment of the presentinvention, if the velocity is lower than the first threshold value, thesynthesizing unit 26 generates the operation quantity of the targetobject using only the first operation quantity out of the first andsecond operation quantities.

FIG. 12 is a flowchart illustrating carriage motor driving control ofreciprocally moving the carriage by operating only the second controlunit in accordance with the carriage velocity. Note that in FIG. 12, thesame step numbers denote the same processing steps as those describedwith reference to FIG. 11 and a description thereof will be omitted.

Referring to FIG. 12, the processes associated with the state quantityestimation unit 25 are omitted from the flowchart shown in FIG. 11, andonly steps S1, S3, S4, S5, S10, S11, and S12 are executed.

4. Explanation of Another Application Example of Feedback Control

The present invention is applicable to any control of moving an objectby driving the motor, as described above. Therefore, the presentinvention is applicable to, for example, control of the scanner motorthat moves the CCD sensor or the CIS of the scanner apparatus having asingle function or the scanner unit of a multi-function printer (MFP).

To ensure the image reading performance, the scanner unit needs toacquire an image signal by matching the movement quantity of the scannerunit and the light source lighting timing of the CCD sensor or the CIS.Since the light source lighting timing generally assumes that the movingvelocity of the scanner unit is constant, it is important to suppressthe velocity vibration of the scanner unit. Therefore, since thevibration target to be suppressed is the moving velocity of the scannerunit, the combination of the state quantities of the velocity and theacceleration is applied to the above-described second control unit.Basically, control is performed with the same arrangement as thecarriage control arrangement described with reference to FIG. 9.

This can suppress a micro-vibration at a high-frequency of the scannerunit, which cannot be suppressed by only the conventional control, andimprove the feedback control traceability. As a result, high-qualityimage reading can be achieved.

The present invention is also applicable to conveyance roller drivingcontrol of the printing apparatus described with reference to FIGS. 7and 8. The printing apparatus rotates the conveyance roller for eachcarriage scanning operation to intermittently convey the print medium.To suppress a conveyance quantity vibration at this time, feedbackcontrol according to the present invention can be applied. In this case,since the control target object is the conveyance quantity of the printmedium, the rotation quantity and rotational velocity of the conveyanceroller are respectively input as the first and second state quantitiesto the above-described second control unit.

This can implement more precise conveyance control.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2018-087539, filed Apr. 27, 2018, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An electric apparatus for controlling movement of a target object, comprising: a detector configured to detect the movement of the target object; a first estimation unit configured to estimate, based on a detection signal output from the detector, a control quantity for performing first feedback control for the target object during a first period; a second estimation unit configured to estimate, based on the detection signal output from the detector, a velocity of the target object and an acceleration obtained by time differentiation of the velocity in order to perform second feedback control for the target object during a second period shorter than the first period; a first generation unit configured to generate a first operation quantity for the first feedback control based on the control quantity estimated by the first estimation unit; a second generation unit configured to generate a second operation quantity for the second feedback control based on the velocity and the acceleration estimated by the second estimation unit; and a synthesizing unit configured to generate an operation quantity on the target object, wherein if one of a predetermined target value and the velocity of the target object estimated by the second estimation unit is higher than a first threshold value for the velocity, the synthesizing unit generates the operation quantity on the target object based on the first operation quantity and the second operation quantity, and if one of the target value and the velocity of the target object is lower than the first threshold value, the synthesizing unit generates the operation quantity on the target object using only the first operation quantity from among the first operation quantity and the second operation quantity, the first generation unit is implemented by executing a program by a processor, and the first estimation unit, the second estimation unit, the second generation unit, and the synthesizing unit are implemented by an ASIC.
 2. The apparatus according to claim 1, wherein the second estimation unit sets an estimation frequency of the acceleration when the velocity of the target object is lower than a second threshold value higher than the first threshold value to be higher than an estimation frequency of the acceleration when the velocity of the target object is higher than the second threshold value.
 3. The apparatus according to claim 2, wherein if one of the target value and the velocity of the target object is lower than the first threshold value, an output from the second generation unit becomes zero, and the synthesizing unit generates the operation quantity on the target object using only the first operation quantity from among the first operation quantity and the second operation quantity.
 4. The apparatus according to claim 3, wherein if one of the target value and the velocity of the target object is lower than the first threshold value, the output from the second generation unit becomes zero by not generating the second operation quantity by the second generation unit, and the movement of the target object is controlled using only the first feedback control from among the first feedback control and the second feedback control.
 5. The apparatus according to claim 2, wherein the electric apparatus comprises a printing apparatus configured to print on a print medium by a printhead by reciprocally moving a carriage mounted with the printhead, and the target object comprises the carriage.
 6. The apparatus according to claim 5, wherein the velocity comprises a velocity of the carriage, and the acceleration comprises an acceleration of the carriage.
 7. The apparatus according to claim 5, wherein the detector includes an encoder sensor configured to detect a position of the carriage, and the second estimation unit estimates a velocity of the carriage by measuring an edge interval of an encoder signal pulse output from the encoder sensor.
 8. The apparatus according to claim 7, wherein if the velocity of the carriage is lower than the second threshold value, the second estimation unit estimates the velocity of the carriage using a leading edge and a trailing edge of each of an A-phase encoder signal pulse and a B-phase encoder signal pulse, and if the velocity of the carriage is higher than the second threshold value, the second estimation unit estimates the velocity of the carriage using one edge of one of the A-phase encoder signal pulse and the B-phase encoder signal pulse.
 9. The apparatus according to claim 1, wherein the electric apparatus comprises one of a scanner apparatus configured to read an image of an original by a scanner unit mounted with a CIS or a CCD sensor by moving the scanner unit, and a multi-function printer obtained by providing the scanner apparatus in a printing apparatus for printing on a print medium by a printhead by reciprocally moving a carriage mounted with the printhead, and the target object comprises the scanner unit.
 10. The apparatus according to claim 1, wherein the synthesizing unit generates the operation quantity during a period from start to stop of the movement of the target obj ect.
 11. A control method for an electric apparatus for controlling movement of a target object, comprising: detecting the movement of the target object; estimating, based on a detection signal acquired in the detecting, a control quantity for performing first feedback control for the target object during a first period; estimating, based on the detection signal acquired in the detecting, a velocity of the target object and an acceleration obtained by time differentiation of the velocity in order to perform second feedback control for the target object during a second period shorter than the first period; generating a first operation quantity for the first feedback control based on the estimated control quantity; generating a second operation quantity for the second feedback control based on the estimated velocity and the estimated acceleration; and generating an operation quantity on the target object, wherein in the generating the operation quantity, if one of a predetermined target value and the estimated velocity of the target object is higher than a first threshold value for the velocity, the operation quantity on the target object is generated based on the first operation quantity and the second operation quantity, and if one of the target value and the velocity of the target object is lower than the first threshold value, the operation quantity on the target object is generated using only the first operation quantity from among the first operation quantity and the second operation quantity.
 12. The method according to claim 11, wherein in the estimating the velocity and the acceleration, an estimation frequency of the acceleration when the velocity of the target object is lower than a second threshold value higher than the first threshold value is set to be higher than an estimation frequency of the acceleration when the velocity of the target object is higher than the second threshold value.
 13. The method according to claim 12, wherein if one of the target value and the velocity of the target object is lower than the first threshold value, an output in the generating the second operation quantity becomes zero, and the operation quantity on the target object is generated using only the first operation quantity from among the first operation quantity and the second operation quantity.
 14. The method according to claim 13, wherein if one of the target value and the velocity of the target object is lower than the first threshold value, the output in the generating the second operation quantity becomes zero by not generating the second operation quantity, and the movement of the target object is controlled using only the first feedback control from among the first feedback control and the second feedback control.
 15. The method according to claim 11, wherein the operation quantity is generated during a period from start to stop of the movement of the target object. 